The two-dimensional silicon backbone structure of planar polysilane and Wöhler siloxene is responsible for their exciting luminescing properties. We have prepared single crystals of siloxene by a topotactic reaction from crystalline CaSi 2 . The chemical composition was determined as ͓Si 6 H 3 ͑OH͒ 3 ͔ n . The x-ray crystal structure analysis identifies the so-called Wöhler siloxene as 2D-poly͓1,3,5-trihydroxocyclohexasilane͔. Polysilane exhibits the same structural properties but with a chemical composition ͓Si 6 H 6 ͔ n . The optical properties ͑infrared transmission, photoluminescence, excitation spectroscopy͒ of these well-defined materials are presented. A heat treatment above 350°C in vacuum of Wöhler siloxene results in a destruction of the planar ϱ 2 ͓Si Ϫ ͔ structure by internal rearrangements, which is evidenced by the x-ray-diffraction pattern and characteristic changes in the optical spectra. The involvement of Wöhler siloxene in the optical properties of porous Si is critically reviewed.

The crystal structures of the S-phase with a composition of Cu0.~~Inl.l&3e2.00 and of a Cupoor p-phase with a composition of Cu0.3&11.20Se2.00, both quenched from 750 O C , have been determined with single crystals. The S-phase crystallizes with a = 576.2(4) pm in the ZnStype structure (space group F43m). the /?-phase with a = 5 7 5 4 3 ) pm, c = 1152.0(4) pm and Z = 4 in a new structure type for tetrahedral structures with the space group PZ2c. In both compounds the cations are statistically distributed together with vacancies. The number of vacancies is estimated from the crystal structure analyses and results to be (Cu0.54(2)Inl.l5(2)00.30(2))s~~ for the amphase and (C~0.36Inl.09n0.55) (Sel.80O0.20) for the Cu-poor /?-phase.Die Kristallstrukturen der &Phase mit der Zusammensetzung Cu0.46Inl.~dSe2.00 und einer Cu-armen @-Phase mit der Zusammensetzung Cuo.39Inl.zoSe2.00 wurden mit Einkristallen bestimmt. Beide Phasen wurden von 750 O C abgeschreckt. Die S-Phase kristallisiert mit a = 576.2(4) pm im ZnS-Typ (Raumgruppe F&3m), die 8-Phase mit a = 576.5(3) pm, c = 1152.0(4) pm und 2 = 4 in der Raumgruppe PZ2c in einem neuen Strukturtyp fur Tetraederstrukturen. I n beiden Verbindungen sind die Kationen partiell statistisch verteilt mit Leerstellen. Die Zahl der Leerstellen wurde aus den Strukturbestimmungen abgeschatzt: (C~0.54(2)Inl.l5(2)O3.30(2)) Se, f* die &Phase und (Cuo.dn1.0900.55) (Sel.soOo.z~) fur die Cu-arme 8-Phase.

The management of de Quervain's disease (DD) is nonoperative in the first instance, but surgery should be considered if conservative measures fail. We present the long-term results of operative treatment of DD. From July 1988 to July 1998, 94 consecutive patients with DD were treated operatively by a single surgeon. There were 80 women and 14 men. Average age at the time of operation was 47.4 years (range 22-76). The right wrist was involved in 43 cases, the left in 51 cases. All operations were done under tourniquet control with local infiltration anaesthesia using a longitudinal incision and partial resection of the extensor ligament. There were six perioperative complications, including one superficial wound infection, one delayed wound healing, and four transient lesions of the radial nerve. A successful outcome was achieved in all cases with negative Finkelstein's test. Simple decompression of both tendons and partial resection of the extensor ligament with a maximum of 3 mm can be recommended in operative treatment of DD with excellent long-term results.

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